This type of radiation detector is used in emission computed tomography (ECT: Emission Computed Tomography) equipment to detect radiation (such as gamma rays) emitted from radiopharmaceutical that is administered to a subject and is localized to a site of interest for obtaining sectional images of the site of interest in the subject showing radiopharmaceutical distributions. Typical ECT equipment includes, for example, a PET (Positron Emission Tomography) device and an SPECT (Single Photon Emission Computed Tomography) device.
A PET device will be described by way of example. The PET device has a detector ring with block radiation detectors arranged in a ring shape. The detector ring is provided for surrounding a subject, and allows detection of gamma rays that are transmitted through the subject.
Such radiation detector arranged in the detector ring of the PET device is often equipped that allows position discrimination in a depth direction of a scintillator provided in the radiation detector for improved resolution. Particularly, such radiation detector is used, for example, in a PET device set for animals. FIG. 14 is a perspective view showing a construction of a conventional radiation detector. Such radiation detector 50 has scintillation counter crystal layers 52A, 52B, 52C, and 52D in which scintillation counter crystals 51 of rectangular solid are accumulated in two dimensions, and a fluorescence detector 53 with a function of position discrimination that detects fluorescence irradiated from each of the scintillation counter crystal layers 52A, 52B, 52C, and 52D. Here, each of the scintillation counter crystal layers 52A, 52B, 52C, and 52D is laminated in a z-direction to form a scintillator 52 that converts incident radiation into fluorescence. Two or more reflectors 54 are provided in each of the scintillation counter crystal layers 52A, 52B, 52C, and 52D.
A light guide 55 is provided between the scintillator 52 and the fluorescence detector 53 to optically connect the scintillator 52 and the fluorescence detector 53.
The light guide 55 has a solid resin through which fluorescence is transmitted. The solid resin includes inside thereof two or more reflectors 55a. The reflectors 55a are inserted in an aperture of a molding frame 60, and a liquid thermosetting resin 61 is poured into the molding frame 60, as shown in FIG. 15(a), for manufacturing the light guide 55. The thermosetting resin 61 is cured, and thereafter a pressing plug 62 provided in the bottom of the molding frame 60 is pushed in a direction toward the aperture of the molding frame 60 as indicated by an arrow. As a result, the light guide 55 is removed from the molding frame 60 as shown in FIG. 15(b). Subsequently, grinding is performed to both surfaces 63 and 64 of the light guide 55 through which fluorescence is transmitted. When both surfaces 63 and 64 of the light guide 55 is flat, both surfaces 63 and 64 are polished, whereby the light guide 55 is completed (see, for example, Patent Literature 1).    [Patent Literature 1]    Japanese Patent Publication No. 2004-245592